(1) Field of the Invention
This invention relates to an optical image reader, and more particularly to an optical image reader which effects the reading of an image on a given manuscript by moving over the surface of the manuscript an image reading head provided with a plurality of photosensors and enabling the photosensors to discern the image.
(2) Description of the Prior Art
The conventional optical image reader is provided with an image reading head 1 which, as illustrated in the drawing FIG. 9, has eight reflection type photosensors r1-r8 arrayed at regular intervals in the order of their ordinal numbers in a direction perpendicular to the direction of reading.
The image reading head 1 constructed as described above is intermittently moved over a manuscript face 2 so as to read sequentially the image informations falling on a plurality of rows each consisting of read points coinciding with the aforementioned photosensors r1-r8. To be more specific, it moves by alternately repeating stops (for reading) and moves (to transfer to the next rows) leftwardly over the manuscript face 2 so as to read the image information at the read points a1 . . . an, .about., h1 . . . hn in the successive rows. The intermittent movement of the image reading head 1 relies on the use of a microcomputer 3 and a stepper motor 5, as illustrated in the drawing FIG. 10. Specifically, based on the control signals issued from the microcomputer 3 via a motor drive circuit 4, the stepping motor 5 is intermittently driven and a conveyor belt 6 to which the head 1 is attached is intermittently moved by the stepping motor 5.
In the optical image reader operated by the principle described above, while the image reading motion is very quick, the time the head 1 requires between the moment it starts a stopping motion and the moment it completes the stopping motion is too long to be ignored and is liable to lengthen the overall operation of the head 1. Moreover, since the head 1 is moved intermittently by alternating the moves and stops, the optical image reader does not have much room for further improvement in the reading speed. The heavy power consumption by the stepper motor 5 has also raised a problem from an economic point of view.